Intrathecal Baclofen Therapy

Overview

Spasticity is a motor disorder characterized by tight or stiff muscles that may interfere with voluntary muscle movements.
It is seen in patients with multiple sclerosis (MS), spinal cord injury (SCI), cerebral palsy (CP), and acquired brain injury (ABI). Increased tone and spasm reduces mobility and independence, and interferes with activities of daily living, continence and sleep patterns. Spasticity may also be associated with significant pain or discomfort, skin breakdown, contractures, sleep disorders and difficulty in transfer.
Spasticity is not always detrimental. Spasticity provides posture and tone to a limb that can assist with weight bearing, even if the patient cannot walk. However, excessive tone may also interfere with activities. Therefore, it is only when spasticity interferes with function or puts the patient at risk of hurting himself or herself that it needs to be treated.
Goals of treatment are to decrease spasticity in order to improve range of motion, facilitate movement, reduce energy expenditure and reduce risk of contractures. Existing treatments include physical therapy, oral medications, injections of phenol or botulinum toxin, or surgical intervention.

Pharmacology
Baclofen is the oral drug most frequently prescribed for spasticity.
Baclofen is a

  • a GABA analogue
  • 4-amino-3-(4-chlorophenyl)-butanoic acid.
  • It is a muscle relaxant and antispasticity drug.
  • Oral bioavailability is less due to limited lipid solubility, resulting in low concentration of the drug in the CSF.
  • It is absorbed well in the GIT but does on cross the blood brain barrier.
  • In order to bypass the oral route, baclofen may be administered intrathecally by infusion directly to the CNS.
  • Oral dose: 30-60mg
  • CSF level: 12 to 96 mcg
  • Onset: 30min to 1hour
  • Peak: -4hrs
  • Duration of action: -8hrs
  • Renal clearance: 10-85%

Adverse effects
Sedation
Excessive weakness
Dizziness
Mental confusion
Somnolence
The incidence of adverse effects is reported to range from 10% to 75%.
Adverse effects appear to be dose-related and may be minimized by initiating treatment at a low dose and gradually titrating upwards.

Advantages of intrathecal baclofen infusion:

  • Direct drug administration to the cerebrospinal fluid (CSF)
  • The central side effects of oral baclofen, such as drowsiness or confusion, appear to be minimized with intrathecal administration.
  • Intrathecal administration can use concentrations of baclofen of less than one hundredth of those used orally.
  • Adjustable/programmable continuous infusion makes it possible to finely titrate patients’ doses and to vary the doses over the hours of the day. For example, the dose can be relatively low to give the patients the extensor tone needed for ambulation during the day and increased at night, thereby improving quality of sleep.
  • Reversible (in contrast to surgery).
  • A patient who is a candidate for intrathecal baclofen infusion must have no contraindications to the insertion of an intrathecal catheter (e.g., anticoagulant therapy, coagulopathy, local or systemic infection, anatomical abnormality of the spine).
  • Level 2 evidence supports the effectiveness of intrathecal baclofen infusion for the short-term reduction of severe spasticity in patients who are unresponsive or cannot tolerate oral baclofen
  • Level 3 evidence supports the effectiveness of intrathecal baclofen for the long-term reduction of severe spasticity in patients who are unresponsive or cannot tolerate oral baclofen
  • Level 4 qualitative evidence demonstrates functional improvement for patients who are unresponsive or cannot tolerate oral baclofen
  • Intrathecal baclofen is cost-effective with costs which may or may not be avoided in the Ontario health system
  • True functional use remains to be determined

Patient Selection 

Proper patient selection, meticulous implantation technique, maintenance and continued vigilance are of paramount importance to reduce predictable iatrogenic complications and ensure success. The decision to implant requires careful evaluation of multifaceted therapeutic measures to ensure optimal treatment outcomes. When considering a pump, clinicians must consider comorbidities related to disease and psychosocial factors such as death and dying issues, and life expectancy. Thorough explanation of what the therapy entails and need for continuous commitment for therapy titration on part of the patient and caretaker should be emphasized before proceeding.